# Problem with calibration cube

• Hi,

I have an Hbot with 1.8 degree nema 17 motors. I run them at 32 microsteps. My problem is that i have a hard time calibrating steps/mm. I have modeled a 30/30/30 mm cube and printed it with 3 perimeters, 3 bottom layers and 6 on top. My steps/mm on X and Y were set to 204 and the cube came out 29.7 on X and 29.5 on Y. So i made the calculus ( 30/29.7=1.01 ; 204x1.01=206.4)for X and (30/29.5=1.1069 ; 204x1.0169=207.4) . After this calibration the cube came X=29.7 and Y=29.6

I should mention that before all of this I have calibrated my extruder steps/mm and the cubes were printed with the same material (PLA) at the same temp(205) as when i have performed the extruder calibration. Any ideas?

Thanks.

• The undersize could be caused by under-extrusion or by backlash. If you print a larger cube e.g. 50m or 60mm, you can measure whether the undersize is by the same amount or by the same ratio compared with the smaller cube. If it's the same ratio, the steps/mm needs adjusting, or you can use M579 instead. If it's by the same amount, then the problem is under extrusion or backlash.

• Ok, I'll go for 50x50x50 and post the results.

• So after I printed a calibration cube of 60x60x60 at 205 degree, Pla, 2 perimeters, 3 bottom layers and 6 on top the dimensions are: X=59.2 Y=59.11 Z=60. These are middle measurements. If I measure the bottom I get: X=59.3 Y=59.23

• Taking those measurements together with the ones for the smaller cube, it does sound that your steps/mm are off. Are the belts tight enough?

• The belt is tight and I retighten all the screws, pulleys and so on. I have changed the values for X=220 and Y=230 just to see what's happening. I'll post the result.